In many situations, it is desirable to separate a slurry of raw material into constituent solid and liquid components. For example, while the general composition of municipal waste may be known, any particular gallon of municipal waste may contain a variety of unknown solid or liquid components. Any one of these unknown components may represent an environmental hazard. Accordingly, before municipal waste can be introduced into the environment, it is typically processed to remove any hazardous components. Municipal waste is thus typically processed in a variety of stages designed to remove liquid and solid materials that might be unsuitable for discharge into the environment.
Modern animal husbandry operations such as dairy farms represent another example of a system requiring the processing of a slurry of raw material to remove solid particulates. The present invention is of particular significance in the context of processing waste from a dairy farm, and that application of the present invention will be described in detail herein. However, the principles of the present invention may be applied to any system in which a slurry of raw material must be processed to remove solid components from the slurry.
Dairy farms often require the handling of relatively large numbers of animals in indoor facilities. For example, cows in a dairy operation are kept at least part of the day in stalls defining a stall resting surface. From a cow's perspective, the stall resting surface should be covered with bedding material that is comfortable to lie on, provide uniform support, be cool in the summer, be non-abrasive, and provide confident footing during reclining and rising maneuvers. From the perspective of the operator of the dairy, bedding material should not be detrimental to the health of the cows or the quality of the milk produced by the cows. Sand has been proven to be advantageous as a bedding material and is commonly used in modern dairy operations.
When used as a bedding material, sand often becomes mixed with manure and possibly other contaminants. When cleaning systems are used to remove manure from a diary facility, raw slurry material is formed containing rinse liquids, liquid manure, solids, sand, and possibly other contaminants. If possible, it is desirable to convert components of the raw slurry mixture to usable materials and/or reuse the components of the raw slurry mixture. It is also desirable to allow the sand to be reused.
The present invention relates to the removal of particulate material such as sand from raw slurry mixtures so that the sand may be reused. Removal of sand from the raw slurry material further forms a processed slurry (low sand content) that is more appropriate for further processing operations such as extraction of water, composting, and/or digesting.